How to get variable task picture ?

As part of my work I created a process definition and I deployed it. after I launched an instance of this process. and level of user Task 2 I encountered a problem in the recovery of task picture variable.it always gives me as return value of this variable a type Long. and I do not know the meaning of this value Long.

Out of interest, do you know what type it should be and does it work if you cast the Long to the type that you expect it to be?

I presume it's persisting a binary value. It would help to know what version you're using. You may find it useful to look at Serializing process variables and Activiti User Guide but it's hard to tell if this is useful to you as I'm not sure how you're setting the variable.